This proposal requests support for the purchase of a multiphoton microscope system as a shared resource to benefit major NIH supported projects at the University of Texas at Austin. Laser scanning multiphoton microscopy (LSMM) is a microscopic imaging tool that provides subcellular resolution images with optical sectioning. Because LSMM uses near infrared excitation light, it is able to image deep within thick samples, and due to the nonlinear absorption of photons only at the focal volume, it provides less photobleaching and phototoxicity than conventional confocal microscopy. The proposed multiphoton microscope will be used in three primary areas of research: 1) study of nanovector delivery kinetics, 2) basic disease and tissue physiology, and 3) femtosecond laser-tissue interactions. These projects will have a significant impact in our understanding of drug delivery mechanisms for the treatment of diseases such as cancer, microvasculature hemodynamics in stroke, laser microsurgery of the cornea, the clinical early diagnosis of cancer using optical spectroscopy, tumor metastasis, and differentiation mechanisms of embryonic stem cells. The use of this instrument will impact a wide range of NIH funded projects studying the mechanisms of diseases such as cancer, stroke, and glaucoma. The addition of this instrument to the University of Texas will directly impact the specific NIH funded research projects while also provide a critical research tool to the broader biomedical engineering and science community on campus.